There have been some prior automated bathtub drain valves. See e.g. U.S. Pat. Nos. 1,501,303, 1,924,251, 3,995,651 and 4,042,984. However, valves of this type usually suffer from one or more of the following deficiencies: (1) they cannot be overridden manually (e.g. in case of a power failure or the preference of a particular user is to rely on a manually activated system); (2) they do not permit easy access to the various linkages that connect to the drain valve in order to permit adjustment, installation, or cleaning; and/or 3) they are overly expensive to manufacture, install, or repair. In recent years, some hydraulically activated systems have been developed. While these systems have solved some of the problems, other problems still remain.
Thus, it can be seen that a need exists for an improved automatic drain valve.